<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <script src="loadImage.js"></script>
    <script>
        loadImage({
            bird: './img/bird.png',
            sky: './img/sky.png'
        }, function( imgObj ) {
            console.log( imgObj.bird.width );
            console.log( imgObj.sky.width );
        });
    </script>
</body>
</html>